Slide shutoff for metal flow in a casting process

ABSTRACT

A composite shut-off means for casting moulds, including a sliding closure made of sand and a compressive refractory material. The sliding closure has a passageway passing through it so as to allow the selective passage of molten metal there through, and a filtering means for the molten metal that filters the metal as it passes through the passageway. The means for retaining the sliding closure, are attached to the mould, so that in use, the mould can be closed and sealed by the sliding closure, and removed from the launder.

TECHNICAL FIELD

The present invention relates to the sand casting of metals and more particularly to the use of a composite shut-off that isolates the mould from the launder, and seals the liquid in the casting during the sand moulds rotation through 180°.

BACKGROUND ART

For purposes of explanation, reference will be made to the use of the present invention with respect to the casting of motor cases (engine blocks). It should be understood by those of ordinary skill in the art that the invention is not limited to use in casting engine blocks and can be used in the casting of other products. Cylinder Blocks have traditionally been manufactured as a casting in Cast Iron. Recently Aluminium alloys have become the material of choice for cylinder locks.

While the weight and thermal conduction rates of aluminium have big advantages over cast iron, the actual casting of liquid aluminium is problematic. Conventional gravity pouring of aluminium alloys results in turbulent flow and the manifestation of oxides dispersed through the casting. These oxides often become the failure points for the casting in service. To overcome this problem with oxide formation, counter gravity filling of the liquid aluminium from the bottom of the mould has become the preferred method of casting.

The major problem with counter gravity filling of moulds is the slow production rates, the mould filling system either low pressure or electromagnetic pump need to retain pressure until the casting has solidified. Which for a cylinder block can be up to eight minutes. While the counter gravity filling is desirable, the solidification time and subsequent low productivity are not. To overcome this low productivity problem, methods of disconnecting the mould from the filling system and rotating the mould while the casting is still liquid have been developed. Once the mould and casting are rotated through 1800 the risers which supply liquid metal during the solidification phase of the cast process are on top of the casting and gravity feed the required liquid metal into the contracting casting.

A major problem has been the effective isolation and sealing of the mould, once filled with liquid aluminium, from the launder, so that the mould can be rotated, thereby leaving the launder free to accept a new mould ready for filling.

It is an object of the present invention therefore, to provide a means for effecting sealing of the mould, such that it can be disconnected from the metal source and the pump launder, thereby permitting all post filling actions, including rollover, to be undertaken while the next mould is moving to the cast position. This offers the advantage of greatly reducing casting cycle times.

A further object of the invention is to provide a means for effecting isolation and sealing of the mould so as to prevent drain back of metal from the mould gating into the launder. Known casting methods rotate the mould whilst it is connected to the metal source pump and launder. When the rotation is complete the pressure on the mould is reduced to bias level, which is the top of the launder. This action allows liquid metal in the gating to flow back into the pump launder contaminating the metal to be used in subsequent casting operations.

Yet a further object of the invention is to provide a means for effecting isolation and sealing of the mould, wherein when the slide is in the open position, it is filtering the molten metal passing there through, thereby removing undesirable inclusions.

DISCLOSURE OF THE INVENTION

Thus there is provided according to one form of the present invention, a composite shut-off means for casting moulds, including a sliding closure with at least one passageway passing through it, wherein in use, when in a first open position the passageway is positioned so as to allow the passage of molten metal there through, into the mould, and in a second dosed position, the molten metal is unable to pass through the passageway and the sliding closure seals the mould, preventing the entry of molten metal into the mould.

In a further form, the invention may be said to lie in a composite shut-off means for casting moulds, including a sliding closure that includes sealing means, and molten metal filtering means, wherein said shut-off means is the interface between the metal source and the mould.

Preferably, the sliding closure is operable by way of sliding it substantially transverse to metal flow.

Preferably, the sliding closure, and the means for retaining said sliding closure, are attached to the mould, so that in use, the mould can be closed and sealed by the sliding closure, and removed from the launder.

Preferably, the sliding closure is a rectangular plate element having an aperture or passageway passing there through.

Preferably, the sliding closure is a composite construction of sand, binding agent and compressive refractory material.

Preferably, the sliding closure sealing means includes a gasket made of compressive refractory material.

Preferably, the sliding closure utilises the compressive properties of the composite refractory material, such that in use, the pressure from the launder compresses the sliding closure, thereby effecting a seal.

Preferably, the filtering means uses either a stainless steel or fibreglass screen covering the aperture or passageway in the sliding closure.

Preferably, the sliding closure is actuated by a pneumatic or hydraulic cylinder.

In a further form, the invention may be said to lie in a method of actuating a composite shut-off means for casting moulds that includes a sliding closure, wherein there is a production system utilising a carousel that retains the mould, in which the motion of the carousel indexing is used rotate the carousel and the mould relative to the sliding closure, which is held in a fixed position via interference with the launder.

In a further form, the invention may be said to lie in a method of actuating a composite shut-off means for casting moulds that includes a sliding closure, wherein the launder is attached to a positionable, and programmable three-axis gantry, and the launder actuates the sliding closure via an interference with the sliding closure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of this invention it will now be described with respect to preferred embodiments which shall be described with the assistance of drawings wherein;

FIG. 1 is a detail top elevation of the shut-off slide,

FIG. 2 is an end elevation of the shut-off slide shown in FIG. 1,

FIG. 3 is a cross-sectional view through a casting mould illustrating the operation of the shut-off slide, wherein the slide is in the open position,

FIG. 4 is a cross-sectional view through the casting mould illustrating the operation of the shut-off slide, wherein the slide is in the closed position, and

FIG. 5 is a cross-sectional view through the casting mould illustrating the mould post separation from the launder, and subsequent inversion.

BEST MODE FOR CARRYING OUT THE INVENTION

There is a sliding closure, or shut-off gate 1 having a passageway or aperture 2 passing there through. The slide is a composite construction of sand 3, binding agent and compressive refractory material 4, and the aperture 2 has a filter screen 5 covering it. This filter screen 5 may be either a stainless steel or fibreglass screen, and its purpose is to remove any undesirable inclusions from the molten metal before they can get into the mould 6, and therefore the cast product. A significant advantage of these composite slides is they can be reclaimed in the same manner as the remainder of the mould 6, post casting.

There is a casting launder 7 which can provide molten metal 8 to the mould via the passageway 2 in the sliding closure 1 when the gate is in the open position 9.

When the sliding closure 1 is in a first open position 9, the passageway 2 is positioned so as to allow the passage of molten metal 8 there through, into the mould 6. When the sliding closure 1 is in a second closed position 10, the molten metal is unable to pass through the passageway and the sliding closure seals the mould, preventing the entry of molten metal into the mould, thereby isolating the mould 6 from the launder 7. The full mould 6 can then be separated from the launder and rotated while a fresh mould 15 is filling.

When in a closed position 10 on the launder, the sliding closure utilises the pressure from the launder to compress the composite refractory material 4 in the sliding closure, thereby effecting the seal discussed in the paragraph above.

The sliding closure 1 can be actuated by either a pneumatic or hydraulic cylinder. Alternatively, it can be opened and closed utilising a carousel that retains the mould 6, in which the motion of the carousel indexing is used rotate the carousel and the mould relative to the sliding closure, which is held in a fixed position via interference with the launder 7.

Another method of actuating the sliding closure, involves attaching the launder 7 to a positionable, and programmable three-axis gantry (not shown); the launder 7 then actuates the sliding closure via an interference with the sliding closure 1.

A further method still of activating the sand slide might make use of a robot that manipulates the sand mould prior, during and after the casting cycle. This robot then would replace the carousal discussed above, in that it is the robot that moves the mould relative to the sliding closure, which is held in place due to the interference with the launder.

Articles such as those described herein would prove to be of considerable benefit in sand casting applications where cycle time for the casting operation is an important consideration.

Throughout this specification then the purpose of the description has been to illustrate the invention and not to limit this. 

1. A composite shut-off means for casting moulds, including a sliding closure with at least one passageway passing through it, wherein in use, when in a first open position the passageway is positioned so as to allow the passage of molten metal there through, into the mould, and in a second closed position, the molten metal is unable to pass through the passageway and the sliding closure seals the mould, preventing the entry of molten metal into the mould.
 2. A composite shut-off means for casting moulds, including a sliding closure that includes sealing means, and molten metal filtering means, wherein said shut-off means is the interface between the metal source and the mould.
 3. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure is operable by way of sliding it substantially transverse to metal flow.
 4. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure, and the means for retaining said sliding closure, are attached to the mould, so that in use, the mould can be closed and sealed by the sliding closure, and removed from the launder.
 5. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure is a rectangular plate element having an aperture or passageway passing there through.
 6. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure is a composite construction of sand, binding agent and compressive refractory material.
 7. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure sealing means includes a gasket made of compressive refractory material.
 8. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure utilises the compressive properties of the composite refractory material, such that in use, the pressure from the launder compresses the sliding closure, thereby effecting a seal.
 9. The composite shut-off means for casting moulds of claim 1, further characterised in that the filtering means uses either a stainless steel or fibreglass screen covering the aperture or passageway in the sliding closure.
 10. The composite shut-off means for casting moulds of claim 1, further characterised in that the sliding closure is actuated by a pneumatic or hydraulic cylinder.
 11. A method of actuating a composite shut-off means for casting moulds that includes a sliding closure, wherein there is a production system utilising a carousel that retains the mould, in which the motion of the carousel indexing is used rotate the carousel and the mould relative to the sliding closure, which is held in a fixed position via interference with the launder.
 12. A method of actuating a composite shut-off means for casting moulds that includes a sliding closure, wherein the launder is attached to a positionable, and programmable three-axis gantry, and the launder actuates the sliding closure via an interference with the sliding closure.
 13. A method of actuating a composite shut-off means for casting moulds that includes a sliding closure, wherein a robot retains, and moves the mould relative to the sliding closure, which is held in a fixed position via interference with the launder.
 14. (canceled)
 15. (canceled)
 16. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure is operable by way of sliding it substantially transverse to metal flow.
 17. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure, and the means for retaining said sliding closure, are attached to the mould, so that in use, the mould can be closed and sealed by the sliding closure, and removed from the launder.
 18. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure is a rectangular plate element having an aperture or passageway passing there through.
 19. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure is a composite construction of sand, binding agent and compressive refractory material.
 20. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure sealing means includes a gasket made of compressive refractory material.
 21. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure utilises the compressive properties of the composite refractory material, such that in use, the pressure from the launder compresses the sliding closure, thereby effecting a seal.
 22. The composite shut-off means for casting moulds of claim 2, further characterised in that the filtering means uses either a stainless steel or fibreglass screen covering the aperture or passageway in the sliding closure.
 23. The composite shut-off means for casting moulds of claim 2, further characterised in that the sliding closure is actuated by a pneumatic or hydraulic cylinder. 